Relative sea level (RSL) is defined as the sea level that is observed with respect to a land-based reference frame.
It is often contrasted with
eustatic sea level
The eustatic sea level (from Greek εὖ ''eû'', "good" and στάσις ''stásis'', "standing") is the distance from the center of the Earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, inc ...
, which is a measure of the total mass or volume of the oceans. Relative sea level can change by the processes changing eustatic sea level (e.g., ice melt and thermal expansion), but also by changes on land such as
subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...
and
isostatic rebound
Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound ...
.
In
sequence stratigraphy
In mathematics, a sequence is an enumerated collection of mathematical object, objects in which repetitions are allowed and order theory, order matters. Like a Set (mathematics), set, it contains Element (mathematics), members (also called ''ele ...
, relative sea level is similarly defined as the distance from the ocean surface to the bottom of the sediment on the ocean floor.
Therefore, relative sea level is independent of the thickness of the sediment layer at the bottom of the ocean, which makes it a different concept than
water depth
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms ( ...
.
References
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